Sublimation timing switch



NOV. 15, 1966 WILSON ETAL 3,286,064

SUBLIMATION TIMING SWITCH Filed March 31. 1965 5 Sheets-Sheet lINVENTORS Lou/s Wilson Wilson E. Hull Jacob 0. Steinberg Robert E. Fischel/ 5) WWW ATTORNEY AGENT Nov. 15, 1966 L.. WILSON ETAL SUBLIMATIONTIMING SWITCH Filed March '31. 1965 5 Sheets-Sheet 2 FIG. 2

Nov. 15, 1966 7L. WILSON ETAL SUBLIMATION TIMING SWITCH 5 Sheets-Sheet 3Filed March 31. 1965 United States Patent Ofiice 3,286,064 Patented Nov.15, 1966 SUBLIMATION TIMING SWITCH Louis Wilson, Silver Spring, Md.,Wilson E. Hull, Washington, D.C., and Jacob D. Steinberg, Riverdale, andRobert E. Fischell, Silver Spring, Md., assignors to the United Statesof America as represented by the Secretary of the Navy Filed Mar. 31,1965, Ser. No. 444,469 6 Claims. (Cl. 200-142) The present inventionrelates generally to a timing device and more particularly to asublimation timing switch exhibiting predetermined time delays forsequentially actuatingvarious electrical circuits in a spacecraft afterbeing launched.

An objectof the present invention is to provide for a large number ofsequentially switching operations in a satellite.

Another object of the present invention is to provide 1for reliablemulti-pole operations of a switch in a satelite.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawingswherein:

g FIG. 1 is an exploded perspective view of an embodiment of the presentinvention;

'FIG. 2 is an axial sectional view of the assembled switch;

FIG. 3 is a cross-section on line 33 of FIG. 2;

FIG. 4 is a schematic diagram of a circuit showing the operation of theswitch of the present invention; and

FIG. 5 is a side perspective view of a diflerent embodiment of thepresent invention.

Referring now to the drawings, the elongated tubular I ring-shapedsegmented contact member 29 has a circular metallic band 34 with aseries of longitudinally extending segmented electrical finger contactsfastened to the circumferential edge of the band. The band 34encompasses the outer surface of the thimble member 28 and rests on theupper surface of the outwardly directed flange 33 of the thimble member.The sleeve-shaped member 30 has a downwardly extending skirt 37 forreceiving the thimble-shaped member 28. The lower edge of the skirt 37retains the band 34 of the shorting ring bar 29 on the flange 33 of thethimble member 28. The sleeve member 30 has an upstanding circular rim39 for holding a cylindrical-shaped charge of compressed sublimablematerial. The upper end 41 of the charge 40 presses against a heatedwire mesh 42 by the tensile action of the coil spring retained undercompression between the thimble-shaped member 28 and the bottom wall 14.

An annular holder 43 with a central opening 44 and an undercut circularrecess adjacent to the opening retains the heated wire mesh 42 acrossthe open end of the axial chamber of the housing against the upper end41 of the charge 40. The mesh 42 allows upon sublimation of the materialfor subliming vapors to escape and material to pass therethrough. Anannular spacer extending inwardly beneath the undercut recess of theannular holder rests on the exterior flange 18 of the enclosing wall ofthe housing. In order to achieve more uniform heating of the wire mesh,projecting ears of the wire mesh are wrapped around resistors 47received within the recess 45 of the holder and indentations 48 plastichousing 11 of the switch mechanism supports movable elements within aninterior axial cavity or chamber 12 defined by enclosing wall 13. Abottom wall 14 of the housing closes the axial chamber 12 and hasarecess or pit 15 for receiving a metallic cup-shaped seat 16 therein.The enclosing wall 13 of the housing at the open or top end 17 of theaxial chamber 12 has an outwardly extending surrounding flange 18. Theenclosing wall of the housing has a series of peripherally andlongitudinally spaced slots 19 extending from exterior surface 20 to theinterior surface 21 of the enclosing wall into the chamber of thehousing. The slots or bores 19 of the enclosing wall receive 'solidmetal plugs as electrical terminals 22 as shown in FIGS. 2 and 3. Theterminals 22 with prior attached lead wires 22b are held in place andelectrically insulated from each other by a moldable epoxy resin 220'.The longitudinally separated terminals 22 are arranged in peripherallyaligned sets which are indicated in FIG. 2 as position 1, position 2 andposition 3. Depending upon the particular use of the switch, any numberof positions of the electrical terminals can be incorporated in theenclosing wall.

Within the axial chamber of the elongated housing, a coil spring 23encompasses a stem 24 of a spring guide pin 25 and bears on a base 26 ofthe spring guide pin 25 placed within the seat 16 of the bottom wall.With this arrangement, the spring in operation does not hand away froman axial direction and the lower end of the spring does not scarify thebottom wall of the housing. The upper end of the spring presses againsta plunger movable within the chamber. The plunger includes athimble-shaped insulating member 28, a ring-shaped segmented contactmember or shorting bar 29 and a sleeveshaped member 30. Thethimble-shaped member 28 has an axial recess 31 for receiving the upperend of the coil spring and has an outwardly directed flange 33. The

made within the spacer. Lead wires 49 to the resistors extend throughthe holder for connection to an external battery, not shown. The holderand spacer are retained in tight relationship by fasteners 50 insertedthrough the holder and spacer and secured to the flange 18 of thehousing.

Referring to FIGS. 2 and 3, the finger contacts 35 extend longitudinallyover the skirt 37 of the sleeve-shaped member 30 and have curved ends 51for pressing against the interior surface of the enclosing wall andterminals 22. The finger contacts 35 will press against the terminals 22inserted into the slots of the housing wall depending upon the positionof the plunger within the chamber of the housing. The terminals 22 andfingers 35 have such a size relationship that at least two adjacentfingers will make contact with a terminal so that during operation theswitch will have greater reliability.

The charge of sublimable material 40comprises either camphor,napthalene, biphenyl, benzioc acid or any combination thereof. Thesematerials are compressed under high pressure into the charge orcartridge which then can be either lathed or milled with considerableease and precision. Each of the above-mentioned materials have adiflerent rate of sublimation. At normal atmospheric pressure the rateof sublimation is extremely slow but become more rapid in the vacuum ofspace. In addition, the application of heat to a sublimable materialwill increase its rate of sublimation.

When heat is applied to the device of the present invention, it isdesignated as an active switch. An embodi ment of the holder 43 of FIGS.1 and 2 shows a heated wire mesh 42 secured between the holder 43 andspacer 46 with the upper end of the charge pressing against the mesh. Inorder to eflect a more rapid rate of sublimation, the mesh is connectedto a small silver zinc battery, not shown. The battery supplies enoughcurrent to heat the metallic mesh. Consequently, the material sublimesdue to the lack of pressure in space and the addition of heat applied tothe upper end of the charge.

Another embodiment of an active switch is shown in FIG. in which thehousing of the switch is carried by an angle-shaped metallic support 54.The flange 55 of the support has an opening covered with a wire meshsimilar to mesh 42. Withthis arrangement the heat of the rocket ormissile casing is transferred to the base of the metallic support 54 andsubsequently to the wire mesh to heat the sublimable material. Since themissile casing exhibits considerable amounts of heat immediately afterlaunching of a missile, the metallic support 54 is insulated from thecasing with a sheet 56 of glass fiber encapsulated epoxy resin to delaythe operation of the switch to a later desired time of missile flight.

In place of a wire mesh, a perforated sheet of carbon of knownresistivity could be used. In this case, the carbon sheet would absorbheat from the environment and apply it to the top end of the charge ofmaterial.

If the switch is to be subjected only to the vacuum of space, then thepurpose of the wire mesh is to retain the charge of sublimable materialin place. The switch is then known as a passive one. The rate ofsublimation of a passive switch could be delayed on the order of yearsby requiring the subliming vapor to pass through a series of cavitieseach with a small orifice before reaching the vacuum of space.

If the switch is to operate at higher temperatures, the

synthetic plastic or nylon material of the housing 11, thimble 28,sleeve 30 and holder 43 can be made of ceramic or other compositions.Referring now to FIG. 4, the operation of the switch in a satellite isillustrated. When the material of the charge sublimes from a solid to agas, the spring 23 moves the plunger 27 holding the finger contacts 35from an initial position pressed against terminals 22 in position 1.Upon continued sublimation, the finger contacts 35 make connectionsequentially with the terminals 22 at positions 2 and 3.

The schematic of FIG. 4 shows the finger contacts 35 at position 1-grounding through band 34, squibs 58 and 59 during the launching phaseof a missile or satellite. After a predetermined interval of timedepending upon the rate of sublimation of the charge, the fingercontacts 35 at position 2 connect the battery 60 attached to one of theterminals at position 2 to a squib 58 attached to another of theterminals at position 2. Likewise, the operation is the same at position3 to connect a battery 61 to squib 59. In actual use more than oneterminal is connected to the same electrical circuit so that reliabilityof the switch is insured.

The device of the present invention can be used to initiate separationof a payload from a rocket or to separate multiple payloads from eachother. The device has been used as a back-up switch for initiatingseparation in event the rockets programmer failed to provide the payloadseparation signal. Other uses of the switch are possible such as turningon high voltage for a particular satellite experiment.

The switch of the present invention shows use .of a multi-pole operationby the number of terminals and segmented finger contacts. The number ofsequentially switching operations is determined by the number of alignedposition of the terminals. Another variation for increasing the numberof switching operations is to make the band 34 of contact member 27 withinsulated ele- What is. claimed is:

1. A timing switch in a missile or satellite comprising insulatinghousing means having closed end means and open end means and having aplurality of longitudinally separated series of peripherally spacedterminalmeans between said closed and open end means;

carrying means being positioned within said housing means between saidclosed and open end means, said carrying means for' sliding sequentiallyand longitudinally from one of said separated series to another of saidseparated series of peripherally spaced terminal means and havingelectrical shorting means for connecting said peripherally spacedterminal means of one of said longitudinally separated series of saidspaced terminal means;

sublimable means being positioned between said open end means and saidcarrying means within said housing means and abutting againstsaidcarrying means;

resilient means being positioned within said housing means between saidclosed end means and said carrying means for loading said carrying meansand said sublimable means;

holding means attached to said housing means at said open end means forretaining said sublimable means against said carrying means andmaintaining said resilient means within said housing means bearingagainst said closed end means of said housing means and said carryingmeans whereby upon sublimation of sublimable means due to the vacuum ofspace, said resilient means expand longitudinally and move said carryingmeans enabling said electrical shorting means to make contactsequentially with 7 said longitudinally separated terminal means.

2. A timing switch of claim 1 in which said holding means comprisesheating means in the form of a wire 1 mesh for retaining said sublimablemeans and for accepting anelectrical current for heating to saidsublimable means to increase the rate of sublimation of said subliamablemeans. a

3. A timing switch for a satellite for initiating elec trical circuitssequentially according to predetermined ments to isolate certain fingersso that a circuit is only I connected between any two adjacentterminals.

The intervals of time during which the switch mechanism operates isdetermined by the rate of sublimation of the material used, the lengthof the sublimable charge, the temperature and pressure of theenvironment and a combination of any of these.

Obviously many modifications and variations of th present invention arepossible in the light of the above teachings. Itris therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

time delay intervals after launching of a satellite into spacecomprising insulating housing means with an enclosing wall havingexterior and interior surfaces defining an interior axial chamber withclosed and open ends, said enclosing wall having a plurality oflongitudinally separated series of peripherally spaced terminal meansextending from said exterior surface of said wall through said wall tosaid interior of said wall to said interior chamber; sliding means beingpositioned within said chamber of said housing means, between saidclosed and open ends, said sliding means having electrical shortingmeans with a plurality of segmented fingers for' pressing against saidinterior surface of said enclosing wall and said terminal means;

sublimable means being positioned between said open end and said slidingmeans within said chamber' axially abutting against said sliding means;

resilient means being positioned within said chamber between said closedend and said sliding means for loading said sliding means and saidsublimable means;

holding means attached to said housing means at said open end forretaining said sublimable means against said sliding means andmaintaining said resilient means within said chamber bearing againstsaid closed end of-said housing means and said sliding means wherebyupon sublimation of sublimable means due to the lack of pressure afterlaunching a satellite into space, said resilient means move said slidingmeans enabling said segmented fingers of said ,shorting means to makecontact sequentially with said separated terminal means.

4. A timing switch for a satellite for initiating electrical circuitssequentially according to predetermined time delay intervals afterlaunching a satellite into space comprising insulating housing meanswith an enclosing wall having exterior and interior surfaces defining aninteriof axial chamber with cloi sed and open ends, said enclosing wallhaving a plurality of longitudinally separated series of peripherallyspaced terminals extending from said exterior surface of said wallthrough said wall to said interior surface of said wall to said interiorchamber;

sliding means being positioned within said chamber of said housing meansbetween said closed and open ends, said sliding means having electricalcontact means including a plurality of segmented annularj fingers forpressing against said interior surfact of said enclosing wall and saidspaced terminals; a charge of sublimable material being positionedbetween said open end and said sliding means within said chamber axiallyabuttiiig against said sliding means; resilient means being positionedwithin said chamber between said closed en; and said sliding means forloading said sliding mea and said charge;

guiding means within said chamber abutting against said closed end ofsaid hi ing means and having projecting means extending axially throughsaid resilient means for limiting said resilient means to alongitu'dinally axial movement;

holding" means having screening means attached to said housing means atsaid open end for retaining saidffcharge, said sliding ineans and saidresilient means in an initial position. under compression within saidchamber and said, screening means having openings for allowing theescape of subliming vapors upon sublimation of said charge due to thelack of pressure in space, whereby}; upon sublimation of said chargesaid resilient means-move said segmented fingers "for contactingsequentially said longitudinally separated series of terminals;

5. A timing switch of claim' 4 in which said screening means in form ofa wire mesh for accepting an electrical current for heating said chargeto increase the rate of sublimation of said material.

6. A timing device for a satellite for initiating electrical circuitssequentially according to predetermined time delay intervals afterlaunching a satellite into space comprising insulating housing meanswith an enclosing wall defining axial chamber having an open end, aclosed end, said enclosing wall having a plurality of longitudinallyseparated series of peripherally spaced ter'if'ninals extending throughsaid wall to said chamber s'aid terminals adapted for connection to aseries of Electrical circuits;

sliding means being positioned within said chamber of said housingmeans, said sliding means carrying a metallic ring having a plurality ofsegmented annular fingers for pressing against said enclosing wall and.said spaced terminals, said annular fingers having more than one fingerfor making contact with one of said terminals;

a charge of sublimable material being positioned within said chamberaxially abutting against said sliding means;

resilient means being positioned within said chamber between said closedend and said sliding means for loading said sliding means and saidcharge;

holding means having screening means attached at said open end of saidhousing means for retaining said charge and said sliding means undercompression of said resilient means and for maintaining said metallicrling in alignment with one of said series of said longitudinallyseparated terminals, said screening means having openings for allowingthe escape of subliming vapors of said charge, whereby upon sublimationof said material due to the lack of pressure on; said material, saidcharge decreases in length allowing said ring to contact said otherseries of longitudinally separated terminals for initiating anyelectrical circuits attached to said terminals sequentially dependingupon the rate of sublimation of said material.

References Cited by the Examiner UNITED STATES PATENTS 2,883,492 4/1959Landers 200l42 2,934,628 4/1960 Massar et al 200l42 2,955,179 10/1960Milton et al. 200l42 2,999,912 9/1961 Kincaid et a1. 200l42 BERNARDLA.GILHEANY, Primary Examiner.

H. B. GILSQN, Assistant Examiner.

1. A TIMING SWITCH IN A MISSILE OR SATELLITE COMPRISING INSULATING HOUSING MEANS HAVING CLOSED END MEANS AND OPEN END MEANS AND HAVING A PLURALITY OF LONGITUDINALLY SEPARATED SERIES OF PERIPHERALLY SPACED TERMINAL MEANS BETWEEN SAID CLOSED AND OPEN END MEANS; CARRYING MEANS BEING POSITIONED WITHIN SAID HOUSING MEANS BETWEEN SAID CLOSED AND OPEN END MEANS, SAID CARRYING MEANS FOR SLIDING SEQUENCIALLY AND LONGITUDINALLY FROM ONE OF SAID SEPARATED SERIES TO ANOTHER OF SAID SEPARATED SERIES OF PERIPHERALLY SPACED TERMINAL MEANS AND HAVING ELECTRICAL SHORTING MEANS FOR CONNECTING SAID PERIPHERALLY SPACED TERMINAL MEANS OF ONE OF SAID LONGITUDINALLY SEPARATED SERIES OF SAID SPACED TERMINAL MEANS; SUBLIMABLE MEANS BEING POSITIONED BEWEEN SAID OPEN END MEANS AND SAID CARRYING MEANS WITHIN SAID HOUSING MEANS AND ABUTTING AGAINST SAID CARRYING MEANS; RESILIENT MEANS BEING POSITIONED WITHIN SAID HOUSING MEANS BETWEEN SAID CLOSED END MEANS AND SAID CARRYING MEANS FOR LOADING SAID CARRYING MEANS AND SAID SUBLIMABLE MEANS; HOLDING MEANS ATTACHED TO SAID HOUSING MEANS AT SAID OPEN END MEANS FOR RETAINING SAID SUBLIMABLE MEANS AGAINST SAID CARRYING MEANS AND MAINTAINING SAID RESILIENT MEANS WITHIN SAID HOUSING MEANS BEARING AGAINST SAID CLOSED END MEANS OF SAID HOUSING MEANS AND SAID CARRYING MEANS WHEREBY UPON SUBLIMATION OF SUBLIMABLE MEANS DUE TO THE VACUUM OF SPACE, SAID RESILIENT MEANS EXPAND LONGITUDINALLY AND MOVE SAID CARRYING MEANS ENABLING SAID ELECTRICAL SHORTING MEANS TO MAKE CONTACT SEQUENTIALLY WITH SAID LONGITUDINALLY SEPARATED TERMINAL MEANS. 